Hi,

On Tue, 18 Aug 2020, Junio C Hamano wrote:

> René Scharfe <l.s.r@web.de> writes:
>
> > Whitespace is ignored when calculating patch IDs.  This is done by
> > removing all whitespace from diff lines before hashing them, including
> > a newline at the end of a file.  If that newline is missing, however,
> > diff reports that fact in a separate line containing "\ No newline at
> > end of file\n", and this marker is hashed like a context line.
>
> Ah, ouch.
>
> > This goes against our goal of making patch IDs independent of
> > whitespace.  Use the same heuristic that 2485eab55cc (git-patch-id: do
> > not trip over "no newline" markers, 2011-02-17) added to git patch-id
> > instead and skip diff lines that start with a backslash and a space
> > and are longer than twelve characters.
>
> Good find of previous example.  Excellent.

Yup. Looks good to me, too. Thank you!
Dscho

>
> > Reported-by: Tilman Vogel <tilman.vogel@web.de>
> > Initial-test-by: Tilman Vogel <tilman.vogel@web.de>
> > Signed-off-by: René Scharfe <l.s.r@web.de>
> > ---
> >  diff.c            |  2 ++
> >  t/t3500-cherry.sh | 23 +++++++++++++++++++++++
> >  2 files changed, 25 insertions(+)
>
> Thanks.
>
> > diff --git a/diff.c b/diff.c
> > index f9709de7b45..f175019eb7a 100644
> > --- a/diff.c
> > +++ b/diff.c
> > @@ -6044,6 +6044,8 @@ static void patch_id_consume(void *priv, char *line, unsigned long len)
> >  	struct patch_id_t *data = priv;
> >  	int new_len;
> >
> > +	if (len > 12 && starts_with(line, "\\ "))
> > +		return;
> >  	new_len = remove_space(line, len);
> >
> >  	the_hash_algo->update_fn(data->ctx, line, new_len);
> > diff --git a/t/t3500-cherry.sh b/t/t3500-cherry.sh
> > index f038f34b7c0..2b8d9cb38ed 100755
> > --- a/t/t3500-cherry.sh
> > +++ b/t/t3500-cherry.sh
> > @@ -55,4 +55,27 @@ test_expect_success \
> >       expr "$(echo $(git cherry master my-topic-branch) )" : "+ [^ ]* - .*"
> >  '
> >
> > +test_expect_success 'cherry ignores whitespace' '
> > +	git switch --orphan=upstream-with-space &&
> > +	test_commit initial file &&
> > +	>expect &&
> > +	git switch --create=feature-without-space &&
> > +
> > +	# A spaceless file on the feature branch.  Expect a match upstream.
> > +	printf space >file &&
> > +	git add file &&
> > +	git commit -m"file without space" &&
> > +	git log --format="- %H" -1 >>expect &&
> > +
> > +	# A further change.  Should not match upstream.
> > +	test_commit change file &&
> > +	git log --format="+ %H" -1 >>expect &&
> > +
> > +	git switch upstream-with-space &&
> > +	# Same as the spaceless file, just with spaces and on upstream.
> > +	test_commit "file with space" file "s p a c e" file-with-space &&
> > +	git cherry upstream-with-space feature-without-space >actual &&
> > +	test_cmp expect actual
> > +'
> > +
> >  test_done
> > --
> > 2.28.0
>